Lighting that none used (4)
I believe the answer is:
neon
'lighting' is the definition.
(I've seen this before)
'none used' is the wordplay.
'used' is an anagram indicator.
'none' with letters rearranged gives 'NEON'.
'that' is the link.
(Other definitions for neon that I've seen before include "Could it brighten proceedings" , "Small plant; colour" , "One of the six inert gases" , "illuminating agent" , "Gas used in fluorescent lamps" .)